Very small charged fluid droplets have been found useful for a number of uses including applying coating surfaces and capturing dirt in the air. There are a number of advantages to the use of nano droplets for use in a variety of practical applications. For example generating large numbers of nano droplets can be accomplished from low volumes of fluids therein reducing fluid consumption by devices. Nano droplets also have a large surface area to leads to rapid evaporation and efficient delivery of an adjuvant, such as perfume into the air. Nano droplets are easily assimilated into an air flow and remain suspended in the air flow whereas larger droplets would deposit onto surfaces of air circulation ducts. These benefits have advantages for a range of applications including but not limited to air cleaning, perfume delivery, delivery of actives to the nasal and oral cavities.
Very small fluid droplets of various sizes may be formed by a number of alternatives. One known alternative for producing these small droplets is an apparatus equipped with a wet emitter where water is pumped through nozzles having very fine orifices to yield very small water droplets. U.S. Pat. No. 6,656,253 discloses air cleaning devices designed with this spray system. The device yields a charged spray of semiconducting water droplets having a first polarity that is introduced to the air flow. Dirt or other particulates in the air are electrostatically attracted to and retained by the spray droplets.
It's been found, however, that such systems experience nozzle failures when for example, minute non-dissolved precipitants and, or foreign matter in the fluid clog the nozzles. Even where no solids exist in the fluid, higher fluid viscosity can sufficiently interfere with the fluid flow through the nozzles and fail to create the desired sized droplets. Delivering consistent fluid pressure across a plurality of nozzles when issues such as those above or other exist is a technical challenge faced by those skilled in the art.
Alternative approaches for eliminate nozzle related clogging problems encountered when attempting to produce a reliable supply of very small charged particles include using the principle of dry ionization. Dry ionization eliminates the need for a fluid to create charged particles. Devices functioning on the principle of dry ionization are well known in the prior art and typically comprise two electrodes; one at high voltage and the other at some lower electrical potential. This electrical potential drop between the electrodes is applied to produce an electrical field forming a corona or halo around the high voltage electrode. At the point of formation of the corona, the gas in the space between the two electrodes breaks down and releases electrons or ions that travel directly towards the lower potential electrode. In the case of dry ionization air cleaning devices, the break down of the gas, in this case air, leads to the development of ozone that for a number of reasons, too numerous to mention here, is highly undesirable.